1. Field of the Invention
The present invention relates to a method of regenerating a honeycomb type SCR catalyst which is used in selective catalytic reduction (hereinafter, referred to as SCR). More specifically, the present invention relates to a method of regenerating a honeycomb type SCR catalyst using an air lift loop reactor, by which a remarkably reduced activity of the catalyst due to contamination resulting from poisoning by heavy metal components contained in fly ash produced during a combustion process of fuels in thermoelectric power stations and solid deposition is recovered to a level of catalytic activity before contamination thereof.
2. Description of the Related Art
A removal method of nitrogen oxides (NOx) most widely adopted in large thermoelectric power stations at present is an SCR technique that decomposes nitrogen oxides to be removed into harmless nitrogen and water via a catalytic reaction using ammonia as a reducing agent. The catalysts used in such a method, i.e., SCR catalysts, are of honeycomb-shape, and almost all use titanium dioxide (TiO2) as a supporting material and additionally contain organic and inorganic binders including vanadium (1 to 3%) and tungsten (10 to 20%) as a main ingredient.
Such SCR catalysts experience a continuous decrease in catalytic activity thereof due to poisoning of fly ash contained in exhaust gases and solid deposition, and as a result, their lifetimes are exhausted after use for a predetermined period of time (about 2 to 5 years).
Korean Patent Publication Laid-open No. 2001-0078309 discloses a method of regenerating a catalyst involving cleaning a waste catalyst using an anionic surfactant, non-ionic surfactant, a metal compound or the like. Korean Patent Publication Laid-open No. 2001-0072628 discloses a method of regenerating a noble metal catalyst involving impregnating a catalyst, in which at least one noble metal is supported on an amorphous silica alumina support, with an acid, and subjecting the impregnated catalyst to reduction or oxidation at a temperature of more than 200° C. Korean Patent Publication Laid-open No. 2004-0042667 includes a method of regenerating a catalyst involving washing a surface of a waste catalyst with an alkaline solution as a pretreatment, abrading to remove a surface of the catalyst molded material with an abrasive, and as a last post-treatment, washing the catalyst material with an acid solution and water. U.S. Pat. No. 6,387,836 has proposed a method of regenerating a waste catalyst involving subjecting a waste SCR catalyst to chemical cleaning using fully desalinated water and then drying the catalyst with water-free compressed air or oil.